Vacuum-tube stabilizing means



I Patented Dec.v l5,- 92i5.

UNITE- D STATES ra'rerrr OFFICE.

DONALD'G. LITTLE, OF EDGEWOOD, lPENsYLvANA, ASSIGNOR TO WESTINGHO'USE ELECTRIC & MANUFACTURING COMPANY, CORPORATION OF PENNSYLVANIA.

VACUUM-TUBE STABILIZING IEANS.

Application filed March 1922. Serial No. 540,326'.

/"n al! iclfom. it may concern:

lle 'it know-n that I,- DoNiiLn G. Lrr'rLE, a citizen oi' the United `States, and a resident ci Edgewood, in the county ol' Allegheny.

such design as to admit of the utilization of.

paralielconnected modulating tubes having dissimilar characteristics. l

lt is generally known that vacuum tubes', when employed in parallel relation as modulators or ampliliers, should inve straighb line characteristic curves of'similar slopes at predetermined operating voltage, otherwise unstable operation ensues. In practice, how erer, it is extremely diliicult to manufacture tubes haring suc-h operating characteristics,

especially for power out-puts of 250 Watts and more. v

According to my invention, I provide a f system wherein the power supplied to an oscillation `generator system is modulated by a pair of modulator tubes h ."ig iis: niilar. characteristics. The desired stabilizing result is obtained ln. il'icludine,` adjustable resistors in the leads to the modulat u'tuluplates.

W' ith these and other objects and applications in vieu', my invention further consists in the nature, the mode ot operation and theconstructional details hereinater described and claimed and illustrated iu the accompanying drawing, wherein:

The single ligure is a diagraunnatic view of a wireless transmission system embodying in v invention.

In the drawing, a Well vknown type of vacuum-tube oscillation-generator system 1 isshown as operz'ttivelv associated with an' antenna circuit 2 and with a constant. source of direct-current energy 3 and a modulating system 4. The oscillation generator system comprises Aa three-electrode tube 5 having an anode 6, a grid 7 and a hot cathode 8 suitably disposed therein, the latter being energized high-power wireless transmission iara-llel-associatedv l'rom a direct-carre:u source of `energy `9 through-a resistor 1l. y

A grid-hiament circuit for the tube 5 comprises a biasing condenser l), a grid leali 13 connected in shunt thereto and a portion il of a tuning coil l5 which is serially included in the antenna circuit 2. A platetiia-ment circuit includesl a condenser 1G ot lov.' inipedance to currents ot" radio frequenc)v and a portion 17 ot' the tuning coil The antenna circuit 2, in addition to the tuning coil l5 includes an antenna 1S, a tuning coil l0 and a ground conductor Q1.

The constant source of direct-current en ergy o comprises a direct-current generator 22 and a series-connected reactor Q3. Opposite terminals 2i and ot' said source ot' energy 3" are connected by conductors and Q7, respectively, to the plate (5 and to the filament S of Said vacuum tube 5. A.. ra'dio- 'frequency choke coil 2S .may bc included in the conductor JG to prevent the dissipation olf the raflio-lretpieney energy.`

i pair of modulatortubes 29 and 3l, comprising plate elements and 133, grid elen'1ents-34 and 35, and h ot cathode elements 236 and 37 have their plate and iilanient elements connected to the opposite terminals Qt and of the source ot.' energy' 3 by means of conductors 355' aud B9, respectively. cathodcs und 3T may be energized from a common source of direct-current entngy 4 1 through resistors 4:2 and 43', respectively.

Adjustable .resistors 44 and Ll5 are interposed between the connections of the anodes :B2 and 333, respectively, to conductor 3S. In actual practice, I have found that, when employing.modulator tubes having in'ipedances of approximately 18,000 ohms, the' resistance The het of the resistors iet and 4-5 should be oli the order of 5,000 ohms.

.i conductor i6 serves to connect the grid elements and 35 and the hot-cathode ele` ments 3G and 3T in parallel relation to a biasing source oi energy 47 and a secondary winding 4:8 ot a coupling transformer il).

jin amplifier tube comprises an anode 53,.

a grid electrode 5l and a hot cathode 55, the latter being energized from a direct-current sourceot' energ;v 5G through a resistor 57. A conductor 5S serves -toconnect the anode 53 to the positive terminal of the direct-current generator 22 through a prin'iary winding 59 of the transformer ett) and an adjustableresistor 61, the amplifying effect ment circuit for the amplifier tube 52 includes a biasing source of energy 63 and a secondary winding 64 of a modulating transformer 65, thevprimary Winding 66 of which is included in a circuit which may also contain a direct-current source of energy 67 and a microphone transmitter 68.

The resistors l.Maand 4,5 are'adjusted to such value asv to cause the characteristic curves of the modulator tubes 29 and 31 to have similar slopes at the loptimum operating voltage, thus eliminating the tendency for one tube to take the Whole load.

Upon speaking into the microphone transmitter 68, variable potentials are subsequently impressed upon the grid elements 34 and 35 of the modulator tubes 29 and 31, thereby correspondingly modulating the impedances thereof and hence the resulting powerusupply to the oscillation generator system 1.

While 'I' have shown a specific embodi ment of my invention, for the purpose of describing the same and illustrating its rality of tube devices in parallel and means.

plate potential I principles of operation,l it is apparentthat various changes and modications maylbe lmade therein Without, -de'partir'1g fron; the spirit of my invention; I I desire, therefore,Y that only such limitations shall be imposed thereon as lare specifically set forth in theappended claims or demanded by the prior art. f

II claim as myx vention: 1. In a radio sending device, a generato and a modulator operatively associated therewith, said modulator including a plufor separately adjusting the of each oflsald tube devices.'

2. Ina radio'sending device, a source of energy,va vacuum vtube oscillation generator energized therefrom anda modulator diverting varying amounts of energy from said generator, said modulator including a plurality of tubes, each having a plate circuit, said plate circuits being in parallel and individually adjustable impedances, one in eachv oi' said plate circuits.

3.' In `la radio sending device, a source of energy, a vacuum tube oscillation generator energized therefrom and a modulator diverting varying amounts of-energy from said generator, said modulator including a plurality of three-electrode vacuum tubes having their cathodes connected together, their grids connected together and connections from their anodes to a common point, said last named connections including individuallyadjustable resistances,l one for the anode of eachv of said vacuum tubes.

.4. In aradio sending device, a source of energy, 4a vacuum tube oscillation generator energized therefrom and a modulator divertingl varying amounts of energy from said generator, said modulator including a plurality of three-electrode vacuum tubes having theircathodes connected together, and their grids connected together, .a signal controlled device controlling all of said grids simultaneously, and means including a common connection vand a plurality of separately adjustable resistances, one. for each of Said tubes, for individually adjusting the plate voltage of each tube, vvhereby'v the tubes may be, iven characteristics suiiciently alike to cn le said 4tubes to Work together in parallel for'fmodulating the output of said generator in accordance with the signals.

In' testimony whereof, I have hereunto subscribed my name this 25th day of February 1922. Y

. DONALD G.- LITTLE. 

